Modular Assembly Having Press-Fit Fastener Holes

ABSTRACT

A modular assembly having a press-fit fastener hole. The press-fit fastener hole may include a plurality of lobe regions and a plurality of contact regions that may be spaced between lobe regions for a press-fit engagement with a fastener. The fastener may have a first diameter and the contact regions collectively may define an imaginary second diameter that is less than or equal to the first diameter.

REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Ser. No. 61/768,916 filed on Feb. 25, 2013, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to fasteners, and more specifically, to fasteners that may be used to attach different modules or sub-assemblies together, such as a vehicle oil pan to an engine block.

BACKGROUND

In manufacturing industries, skilled artisans will appreciate that it is sometimes desirable to partially assemble components to one another using pre-positioned fasteners. This may enable further assembly at a different manufacturing location (e.g., even by a different manufacturer). Conventionally, pre-positioned fasteners include various mechanical locking devices (e.g., split washers, nylon nuts, etc.), threadlocking material (e.g., commercially available Loctite™), or captive fasteners, just to name a few examples. However, these conventional pre-positioned fasteners require extra materials having extra weight and cost—and in some cases, may not retain the fastener's position, the fastener's orientation, or both.

SUMMARY

According to one embodiment, a modular assembly is provided having a press-fit fastener hole. The press-fit fastener hole includes a plurality of lobe regions; and a plurality of contact regions spaced between lobe regions for a press-fit engagement with a fastener having a first diameter, the contact regions collectively defining an imaginary second diameter that is less than or equal to the first diameter.

According to another embodiment, a modular assembly configured to be coupled to another component is provided. The modular assembly includes a pan having a flange with at least one hole therethrough; and at least one fastener press-fitted within the at least one hole. Each of the at least one holes includes: a plurality of lobe regions, and a plurality of contact regions, each contact region being located at an intersection of two or more lobe regions, wherein the press-fit engagement of the fastener and the hole is associated with an inner diameter of the hole as defined by the contact regions and an outer diameter of the fastener.

DRAWINGS

Preferred exemplary embodiments will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein:

FIG. 1 is an exploded perspective view of an engine assembly;

FIGS. 2A and 2B are top views of an exemplary press-fit fastener hole that may be used with the engine assembly of FIG. 1;

FIGS. 3A-3C are side views of a fastener, in this case a bolt, being installed in the exemplary press-fit fastener hole of FIGS. 2A and 2B, where in FIG. 3A the fastener is not yet installed, in FIG. 3B the fastener is partially installed, and in FIG. 3C the fastener is completely installed;

FIG. 3D is a cross-sectional view of the fastener of FIG. 3B;

FIG. 4 is a flowchart illustrating an exemplary method for providing a modular assembly with fasteners pre-installed in press-fit fastener holes;

FIG. 5A is a side view of a fastener and spacer being installed in another exemplary press-fit fastener hole, where the spacer and press-fit fastener hole work together to retain the fastener in place;

FIG. 5B is a partial, cross-sectional view of the fastener, spacer, and press-fit fastener hole of FIG. 5A fully installed in an engine assembly;

FIG. 5C is a top view of the spacer shown in FIG. 5A;

FIGS. 6-11 are top views of other exempla press-fit fastener holes;

FIG. 12A is a side view of a fastener and another spacer being installed in another exemplary press-fit fastener hole, where the spacer and press-fit fastener hole work together to retain the fastener in place;

FIG. 12B is a partial, cross-sectional view of the fastener, spacer, and press-fit fastener hole of FIG. 12A fully installed in an engine assembly; and

FIG. 12C is a top view of the spacer shown in FIG. 12A.

DETAILED DESCRIPTION

Manufacturers today oftentimes require their suppliers to provide them with parts in the form of modules or sub-assemblies (hereafter referred to as modular assemblies), which the manufacturer may then combine with other parts so as to form a larger assembly or even a finished product. In some circumstances, it is desirable for the supplier to provide the modular assembly with fasteners (e.g., bolts, screws, etc.) already in place, so that the manufacturer can simply line up the modular assembly with another part and attach them together with the already provided fasteners. Consider the exemplary engine assembly 10 illustrated in FIG. 1, where an oil pan 12 is provided by a supplier with a number of fasteners 14 already installed and aligned in their respective holes so that the oil pan can be quickly and easily attached to an engine block 16. By receiving the oil pan 12 with the pre-installed fasteners 14 already inserted into the correct holes and ready for attachment, the manufacturer is able to more quickly and efficiently mount the oil pan 12 to the engine block 16. The manufacturer does not, for example, have to maintain its own inventory of bolts, nor does it have to take the time to retrieve a bolt from a storage bin, insert the bolt through the appropriate hole, and align the bolt so that it will mate with a corresponding mounting hole in the engine block bolt pattern. One challenge associated with providing modular assemblies, like the oil pan 12, with fasteners already in place is that, without any feature to the contrary, the fastener or bolt can simply fall out of the hole in the modular assembly or otherwise become misaligned. The press-fit fastener holes described herein are designed to address this challenge.

Engine assembly 10 includes a modular assembly (e.g., an oil pan 12), an engine block 16, and an intervening gasket 18. The oil pan 12 is attached to the underside of the engine block 16 with a number of pre-installed fasteners 14 that are already retained and aligned in press-fit fastener holes 30 located around the perimeter of the oil pan, such as in a mounting flange 32. These fasteners 14 thread into corresponding holes 38 in an engine block mounting flange 36. A thin, complementary shaped gasket 18 is compressed between the oil pan 12 and the engine block 16 and seals a sump 34 located between those two parts, as is widely understood in the art. It should be appreciated that engine assembly 10 is only one potential application or use of the press-fit fastener holes described herein, as they may be used in any application (automotive or non-automotive) where it is desirable to provide a modular assembly with pre-installed fasteners so that the modular assembly can be more easily attached to other parts. Some non-limiting examples of other applications where press-fit fastener holes may be used include: transmission pans and timing belt, chain, gear, cam and/or valve covers; thus, the term pan should be construed broadly to include any suitable type of pan, cover, sump, lid, etc.

Turning now to FIGS. 2A and 2B, the press-fit fastener hole 30 is designed to retain fasteners 14 in place via an interference fit (or press or friction fit) so that when the oil pan is received by a manufacturer from a supplier it is pre-assembled and ready for attachment to the engine block 16. As better shown in FIGS. 2A and 2B, the press-fit hole 30 may be a multi-lobal hole with at least three points or regions of contact or engagement 60 (e.g., 60 a, 60 b, 60 c) so that the hole can provide an interference or press-fit engagement with a fastener 14 that is inserted therein. In the illustrated embodiment, the contact regions 60 a, 60 b, 60 c are cusps, however, as will be explained below, this is merely one embodiment. The contact regions may both retain the position of the fastener (i.e., prevent the bolt from simply falling out of the oil pan) and retain the alignment or orientation of the fastener (i.e., keep the bolt straight or aligned so that it is properly oriented for insertion through holes 40 and 38). The following description is directed to an embodiment where an oil pan 12 is provided with a number of fasteners 14 already pre-installed, but it is also possible to provide an oil pan/gasket combination with fasteners 14 pre-installed. For example, it is possible for the compression limiter holes 40 in gasket 18 to be press-fit fastener holes. In this latter embodiment, the fasteners 14 may be used to maintain the oil pan 12 and gasket 18 together while they are shipped from the supplier to the manufacturer.

In the exemplary embodiment shown in FIG. 2A, the fastener hole 30 may be tri-lobular—i.e., having a shape defined by three lobe regions 62 (e.g., 62 a, 62 b, 62 c). The lobe regions 62 may be adjacent to one another, and along an interior surface 64 of the hole 30, each lobe region may meet at contact regions 60 (e.g., the cusps each having a radially, inwardly directed point or index). In one embodiment, the contact regions 60 define an imaginary circular, inner diameter D_(3A) (e.g., from about 6 mm-10 mm) which corresponds to the diameter of the fastener, and the lobe regions 62 are circumscribed within an imaginary circular, outer diameter D_(3B) (e.g., from about 8 mm-12 mm). In one particular embodiment shown in FIG. 2B, the shape of the tri-lobular hole may be defined by three overlapping circles (a, b, c), and some of the points where the circles a, b, and c intersect may coincide with the contact regions 60. It is possible for the diameter of at least one of the circles a, b, and c (e.g., respective diameters D_(3a), D_(3b), or D_(3c)) to be equal to the inner diameter D_(3A) of the fastener hole, or in another embodiment the diameter of all the circles a, b, and c may be equal to or within 5% of the diameter D_(3A) (e.g., D_(3A)=D_(3a)=D_(3b)=D_(3c)). Further, it is not necessary that the lobe regions 62 be circular, as they could be oval or some other suitable shape.

As shown in FIG. 3A, the fastener 14 which is to be received in the press-fit fastener hole 30 is an attachment feature, such as a bolt or a screw, that is used to securely mount the oil pan 12 and gasket 18 to the underside of the engine block 16. In the illustrated embodiment, fastener 14 is a bolt and includes a head portion 80 coupled to a threaded shank portion 82 which extends axially therefrom. The head portion 80 can be larger in diameter than the shank portion 82 so that it does not pass through the hole in which the fastener is inserted and, depending on the particular application, can include any number of engagement features. In the hex bolt example illustrated in FIGS. 3A-3D, the head portion 80 has a hex configuration for engagement by a wrench or the like, but it may alternatively be configured as a carriage bolt, shoulder bolt, lag bolt, lug bolt, head bolt, machine screw, socket screw, set screw, or any other type of suitable fastener.

The shank portion 82 is an elongated shank or shaft that axially extends away from the head portion 80 and, according to this example, includes threaded section 84 and a pilot section 86. The exterior or male threads 88 of the threaded section 84 are designed to interact with interior or female threads in the mounting holes 38 in the engine block bolt pattern, as illustrated in FIG. 3C, but this is not necessary as it is also possible for the threaded section 84 to interact with a nut or some other fastening device. The threaded section 84 of the fastener has an outer diameter (OD_(F)) that may, by way of example, be between about 6 mm and 10 mm. In one exemplary embodiment, the outer diameter OD_(F) is 1-10% larger than the inner diameter D_(3A) defined by the contact regions 60 of the tri-lobular hole 30. The pilot section 86, which is optional, has a smooth exterior surface that is smaller in diameter than the threaded section and is intended to help guide the tip of the fastener 14 into the hole in which it is being inserted. In other embodiments, the shank portion 82 does not include a pilot section and is threaded all the way to its distal end. The fastener 14 can be installed to either a threaded blind or through hole in the mating component.

The fastener 14 may have various sizes, dimensions, configurations, material compositions, etc. and may be any type of known bolt, screw or the like. For example, the length, the thread count, the threads per inch (TPI), the pitch, the lead, the units (Metric or English), the head or shank portion configuration, or any other suitable parameter may vary according to the particular application in which the fastener 14 is being used. Although the fastener described herein is not limited to any one type of fastener or bolt, the exemplary fastener 14 is an M6 or M8 bolt. Fastener 14 may be made of various metals (or metal alloys), plastics, or even ceramics, and the fastener may or may not be coated (e.g., zinc plating, galvanizing, chrome plating, etc.), to cite a few examples.

In order for the interference fit to adequately retain the fastener 14 in the press-fit fastener hole 30 (and adequately retain its alignment), the engagement between the contact regions 60 and the threads 88 of the fastener 14 should adequately support the weight of the fastener 14 once it is located within the hole 30; if it does not, the bolt could simply fall back through the hole (e.g., at the time of engagement or later during shipment). Conversely, the engagement between the contact regions 60 and the threads 88 should not be so great as to prevent the bolt from being later fully installed or threaded into the hole 38 of the engine block; e.g., the interference fit between the bolt and the contact regions should not be so great as to damage the threads 88 in such a way that the threads fail to engage the female threads within the engine block hole 38. Also, the engagement should not be so excessive so as to produce high or faulty bolt torque readings at installation. In some embodiments, this engagement should be sufficient to retain a relatively perpendicular alignment of the fastener to the mounting flange 32 so that the manufacturer later does not need to carry out an additional alignment step. In one example, the engagement between the contact regions 60 and the threads 88 of the fastener 14 may result in an angular displacement or misalignment of the bolt (i.e., the angle between a line perpendicular to the surface of the gasket 18 and the central axis of the bolt) that is less than or equal to about 5°; in some instances, it may be less than or equal to 1°. If the angular misalignment is greater than this, the bolt may not line up properly with the corresponding hole 40 in the gasket and the engine block hole 38. In another embodiment (not shown), the contact regions 60 may have female threads thereon sized to receive the fastener threads 88, and the fastener may be rotated into the press-fit fastener hole 30.

FIG. 4 illustrates an exemplary method 100 for providing a modular assembly, in this case an oil pan, from a supplier to a manufacturer where the modular assembly already has one or more pre-installed fasteners 14. Starting with step 101, the supplier receives or maintains a collection of fasteners 14; in this case threaded bolts. Next, the supplier inserts or installs the fasteners 14 into the press-fit fastener holes 30 of a module by press-fitting them therethrough, creating a modular assembly (step 102). In this example, the holes 30 are located in the oil pan mounting flange 32 and the fasteners 14 are inserted to a predetermined depth within the holes. This step may be performed manually or it may be automated with manufacturing equipment. When installing a fastener 14 into a press-fit fastener hole 30, the fastener should be inserted far enough into the hole such that the threads 88 engage each of the contact regions 60. This installation of the fastener 14 into the press-fit fastener hole 30 may automatically align the bolt in an upright and aligned orientation, or the bolt may need to be manipulated so that it is properly aligned. Again, manual or automated means may be used for carrying this out. At this point, the gasket 18 may or may not be provided with the oil pan 12 (e.g., press-fitting the fasteners 14 into the holes 40).

After the various fasteners 14 have been installed in their respective holes, the modular assembly with its pre-installed fasteners may be shipped or otherwise provided to the manufacturer for subsequent assembly operations (step 103). The manufacturer may then attach the oil pan 12 and gasket 18 to the underside of the engine block 16, as described above, and can do so in a more efficient manner due to the fasteners or bolts being already installed, aligned and ready to go.

It should be appreciated that the illustrated engine block, gasket, oil pan, and fasteners are provided only by way of example. The engine block may be any other component or assembly. The oil pan may be various other pans, covers, trays, plates, modular assemblies, etc. And the fastener may also vary as previously described.

Other embodiments of the modular assembly, fastener and/or press-fit fastener holes also exist. In the illustrated examples that follow, like reference numerals indicate like or similar elements or functions.

For example, FIGS. 5A-5C show a fastener 114 and a spacer 120 that may be used for improved alignment of the fastener or bolt. In the embodiment shown, the spacer 120 is a generally hollow cylinder having a first outer diameter OD_(S1) (which may be less than, greater than, or equal to the diameter of the head portion 180 of the fastener; here, it is illustrated as being approximately equal to the diameter of the head portion). A first end 122 of the spacer may be nearest the head portion 180 while a second end 124 may be furthest away from the head portion. The outer diameter OD_(S2) of the second end 124 may be smaller than that of the first end 122, having a shoulder 126 therebetween (i.e., OD_(S2)<OD_(S1)). Multiple gaps 128 may extend axially from the second end 124 towards the shoulder 126 (e.g., the three illustrated gaps may correspond with the contact regions 60 in the hole 30) (see also FIG. 5C). The second outer diameter OD_(S2) may be sized to fit within the press-fit fastener hole 30 in the oil pan mounting flange 32 while the gaps 128 are co-located around the contact regions 60 so that the second end 124 does not interfere with the press fitting of the fastener 114 in the hole 30. In some instances, the second end 124 of the spacer may also be press-fit into the lobe regions 62 of the hole during installation. An inner diameter ID_(S) of the spacer should be large enough so that the spacer can fit over top of the shank portion 182 of the fastener 114.

FIG. 5B is similar to FIG. 3C in that it illustrates the fastener with the spacer 120 fully installed in the engine block 16 securing the oil pan 12 and gasket 18 therebetween. It also illustrates the second outer diameter OD_(S2) within the press-fit fastener hole 30 and the shoulder 126 mated or resting against the flange 32 near the hole 30. This nested relationship may improve the alignment of bolt 114 so that it is more upright, and the spacer 120 may be retained during final installation into the engine block (FIG. 5B) so that the manufacturer does not have to perform an additional step of removing the spacer 120.

In another spacer embodiment shown in FIGS. 12A-12B, the spacer's inner diameter may have a multi-lobular arrangement, similar to that shown in FIGS. 2A and 2B. For example, the inner diameter may have lobes 62 a, 62 b, 62 c and contact regions 60 a, 60 b, 60 c. Similarly, the diameter D_(3A) may be suitably sized for a press-fit engagement with the threads of the fastener 182. In this implementation, the second end 124 may be continuously circular; i.e., it may not have gaps 128 (as described with respect to FIGS. 5A-5C). Furthermore, the holes 30′ in the flange 32 may be circular and sized to receive the second end 124′ of the spacer 120′. In addition, when the spacer is installed into the flange 32, the second end 124′ may be clinched or coined into place, as understood by skilled artisans. Thus, a portion of the second end 124′ may be folded over the opposing side of the flange 32, as shown in FIG. 12A. Of course, means for securing the spacer 120′ are possible as well—including press-fitting the spacer into the hole 30′.

In the implementations shown in FIGS. 5A-5C and 12A-12C, the spacer may improve the grip length of the bolt thereby improving alignment as the axial length of the spacer (120, 120′) may be greater than axial depth of the flange 32. Further, when the oil pan 12 is assembled to the engine block 16, spacer implementations place the fastener 182 in tension thereby enhancing the clamping force on the pan. The spacers may be composed of any suitable material including metal(s) or plastic(s).

In another spacer embodiment shown in FIG. 6, a spacer 620 may have any shape (e.g., circular); and the hole in the mounting flange may have a complementary shape (e.g., circular). The outer diameter of the spacer near the second end 624 may be slightly larger than the diameter of the mounting flange hole so that the spacer may be press-fit therein. While the spacer 620 may be generally cylindrically hollow therethrough, the interior surface 644 of the spacer may have axially extending projections which each extend radially inwardly to a tip or contact region 660. The contact regions 660 may define the diameter D_(3A) which is slightly smaller than the fastener so that the fastener may be press fit therethrough once the spacer 620 is installed in the mounting flange.

In other embodiments, the press-fit fastening holes may have different shapes. And in some instances, the contact regions 60 may be flat rather than angular cusps. For example, in one embodiment shown in FIG. 7, the fastening hole 730 may be triangular and have contact regions 760. Or, for example in FIG. 8, the contact regions 860 may have indexes or tips or projections (e.g., indexes extending from a circular hole 830 in the mounting flange). In other embodiments, the number of contact regions may vary; e.g., there may be four, five, six, or more contact regions. In FIG. 9, four contact regions 960 are illustrated and the hole 930 is square. In FIG. 10, five contact regions 1060 are illustrated and the hole 1030 is star-shaped. And in FIG. 11, six contact regions 1160 are illustrated and the hole 1130 is hexagonal. Thus, as shown in FIGS. 7-11, the lobe regions need not be circular, but may have various shapes and sizes.

Other embodiments may also exist. For example, additional annular retention and alignment features made from low density foam or other suitable materials may be inserted around the bolt to assist with retaining and aligning the bolt within the hole, as described in U.S. patent application Ser. No. 61/807,008 which is hereby incorporated by reference in its entirety.

It is to be understood that the foregoing description is not a definition of the invention, but is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation. 

1. A modular assembly having a press-fit fastener hole, the press-fit fastener hole comprising; a plurality of lobe regions; and a plurality of contact regions spaced between lobe regions for a press-fit engagement with a fastener haying a first diameter, the contact regions collectively defining an imaginary second diameter that is less than or equal to the first diameter.
 2. The press-fit fastener hole of claim 1, wherein the press-fit fastener hole is located in a flange of the modular assembly.
 3. The press-fit fastener hole of claim 2, wherein the press-fit fastener hole has three lobe regions, the lobe regions defined by three overlapping ellipses.
 4. The press-fit fastener hole of claim 2, wherein each of the contact regions include a cusp.
 5. The modular assembly of claim 2, further comprising the fastener having a shank with the first diameter, wherein the shank is slidably received in the press-fit fastener hole, wherein when the shank is located in the press-fit fastener hole, the position and orientation of the fastener are retained.
 6. The modular assembly of claim 5, wherein the fastener shank has a plurality of male threads along its axial length engaging the contact regions, wherein the male threads are adapted to be both press-fit against the contact regions and afterwards be received by female threads.
 7. The modular assembly of claim 5, wherein the first diameter is 1-10% larger than the imaginary second diameter.
 8. The modular assembly of claim 5, wherein the orientation of the fastener shank with respect to the flange is retained within 5 degrees.
 9. The modular assembly of claim 5, further comprising a pan comprising the flange, wherein the pan is one of an oil pan, a transmission pan, a timing belt cover, a chain cover, a gear cover, a cam cover, or a valve cover.
 10. The press-fit fastener hole of claim 1, wherein the press-fit fastener hole is located within a spacer of the modular assembly.
 11. The modular assembly of claim 10, wherein when the fastener is located in the press-fit fastener hole of the spacer, the position and orientation of the fastener are retained.
 12. A modular assembly configured to be coupled to another component, comprising: a pan having a flange with at least one hole therethrough; and at least one fastener press-fitted within the at least one hole, wherein each of the at least one holes includes: a plurality of lobe regions, and a plurality of contact regions, each contact region being located at an intersection of two or more lobe regions, wherein the press-fit engagement of the fastener and the hole is associated with an inner diameter of the hole as defined by the contact regions and an outer diameter of the fastener.
 13. The modular assembly of claim 12, wherein the contact regions are radially inwardly extending cusps.
 14. The modular assembly of claim 12, wherein the at least one fastener is configured for position and orientation retention within the hole until the modular assembly is fixedly coupled to the another component via the at least one fastener.
 15. The modular assembly of claim 14, wherein the orientation of a longitudinal axis of the fastener is retained with respect to the flange within 5 degrees. 